Air blast device with improved ejection conduit

ABSTRACT

The invention relates to an air blast device disposed between an inlet conduit ( 3 ) designed to be connected to a container designed to accumulate a volume of air and an outlet conduit ( 5 ), characterized in that the area (C) of the cross-section of the outlet conduit measured at its distal end is greater then the area (A) of the cross-section of the inlet conduit measured at its end located near the flow control device.

CROSS REFERENCE TO RELATED APPLICATION

The subject matter of this application is related to application Ser.No. 10/443,847 filed concurrently herewith in the name of Herve SIMOENS.entitled “Air Blast Device” and corresponding to French Application No.FR02/06374, filed May 24, 2002, the subject matter of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The invention relates to an air blast device with an improved injectionconduit.

BACKGROUND OF THE INVENTION

In various applications, it is necessary to remove accumulations ofmaterials that impair the proper functioning of the installation.

Such is the case in cement works or bulk materials silos that areemptied by gravity.

To do this, instead of using purely mechanical means like a metal barmanipulated by an individual, it is known to use air blast devices.

The principle of these devices consists of filling a reservoir or acontainer with air at a given pressure and to allow the air to escapesuddenly so as to produce a blast.

Under the effect of the blast, the accumulations of materials are brokenup.

The advantage of these devices consists in the fact that they canfunction automatically and be disposed in places that are not readilyaccessible.

The known devices comprise a device for controlling the flow of agaseous fluid established on a course linking the gaseous fluidaccumulator and possibly an ejection nozzle.

Thus, conventionally, the blast device comprises a body housing a pistonwhose front face closes a so-called outlet port that opens into anoutlet conduit, this body having an inlet conduit that connects it tothe reservoir or container.

Throughout the filling period of the container, the rear face of thispiston is subjected to a pressure that holds the piston over the outlet.

When the pressure maintaining the pressure on the piston is released,the latter suddenly moves back and allows the fluid to pass from thecontainer to the outlet conduit, which may or may not incorporate anozzle.

In the devices known to date, the outlet conduit has a constantcross-section along its longitudinal axis identical to that of the portbetween the container and the body of the device.

However, quite often, the geometry of the outlet conduit is differentalong the axis, i.e., at the level of the area to which the piston isapplied, the cross-section of the outlet conduit is circular, sometimesevolving into an ellipse.

The efficiency of these devices is directly linked to the dischargespeed of the air contained in the reservoir.

This ejection speed specifically depends on the opening speed of thepiston.

Thus, we conceived of making the piston lighter.

To do this, the latter is given the shape of a cup, particularly atruncated one, whose convex front face closes the outlet port and whoseconcave rear face supports a means for guiding it with the body of thedevice.

This guiding means is preferably reduced to a slider that moves inside aguide attached to rear of the body.

This makes it possible both to make the piston lighter and to reducefriction by reducing the guide surfaces.

Particularly for purposes of installing these blast devices, it isconvenient for the inlet conduit that connects the fluid flow controldevice to the container to be approximately perpendicular to the outletconduit.

This also makes it possible to limit the distance between the inlet andthe outlet.

Along its course, there is necessarily a loss of pressure that reducesthe efficiency of the device.

It is of course possible to increase the efficiency of these devices byincreasing the volumetric capacity of the reservoir or by increasing thepressure of the air contained in the reservoir, but this is not alwayspossible, either for economic reasons or because of the installation ofthe blast devices.

Another problem results from the noise produced by the evacuation of theair contained in the rear chamber.

In order to reduce the noise during the emptying of the rear chamber, itis thus known to evacuate the air contained in this chamber, eitherdirectly or indirectly, into the outlet conduit.

To do this, it is known from U.S. Pat. No. 4,201,362 to equip the frontface of the piston with a series of valve disposes one behind the other.

Such an assembly results in an increase in the weight of the main valve,and hence a loss of efficiency in the device.

SUMMARY OF THE INVENTION

The invention proposes to offer a solution for improving the efficiencyof the aforementioned systems.

To this end, the subject of the invention is an air blast devicecomprising an air flow control device disposed between an inlet conduitdesigned to be connected to a container designed to store a volume ofair and an outlet conduit, this blast device being characterized in thatthe area of the cross-section of the outlet conduit measured at itsdistal end is greater than the area of the cross-section of the inletconduit measured at its end located near the flow control device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be clearly understood with the help of the followingdescription given as a nonlimiting example in reference to the attacheddrawing, which schematically represents:

FIG. 1: a view of the end an air blast device,

FIG. 2: a sectional view take along AA of Fig 1.

FIG. 3: a variant of in partial section,

FIGS. 4 through 6: illustrate various details of the blast devicestructure,

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to the drawings, we see an air blast device 1 comprising anair flow control device 2 disposed between an inlet conduit 3 designedto be connected to a container 4 designed to accumulate a volume of airand an outlet conduit 5.

In order to attach the container to the device, it is arranged, forexample, for the inlet conduit of the body of the device to be equippedwith a flange 6.

A second flange 7 is generally provided for connecting the outletconduit to a wall or to a nozzle.

Conventionally, the control device 2 is constituted by a valve 2A which,pressed into a seat 2B, can move away from it in order to allow the aircoming from the container 4 to move freely to the outlet conduit 5,which may incorporate a nozzle, the assembly still being called anoutlet conduit.

In the example represented, the main valve 2A is in the form of a pistonor a truncated cup whose front face 2C presses against a seat 2B.

This front face 2C is therefore located on the convex face of the cup.

This piston or cup closes the entry of the outlet conduit.

As may be seen, the inlet conduit 3 opens laterally into the body 100 ofthe device.

The main valve is translationally guided.

For this purpose, in the example presented, particularly in the case ofthe cup shape, the rear face of the cup supports a slider 10 thatcooperates with a guide 11 presented by the body of the blast device.

This guide is supported by a part 12 of the wall of the body of thedevice that is removable.

In order to fill the container, a controlled air inlet opens:

-   -   either into the rear chamber 13 of the body of the device, and        the clearance between the lateral wall of this chamber and the        cup makes it possible to supply the container with air,    -   or into the inlet conduit, in which case it is still the        aforementioned clearance that makes it possible to supply the        rear chamber so as to apply the piston or the cup.

A double supply of both the rear chamber and the container is also anavailable solution.

Quite often, a means 130 for returning the main valve to its closedposition is provided, but this is not mandatory.

A device 14 makes it possible to evacuate the air contained in the rearchamber in order to move the cup or piston back.

According to one characteristic of the invention, the area C of thecross-section of the outlet conduit measured at its distal end isgreater than the area A of the cross-section of the inlet conduitmeasured at its end located near the flow control device.

The term distal end is understood to mean the end of the outlet conduitfurthest from the cup or piston

Advantageously, a cross-section area B of a cylindrical section of theoutlet conduit measured at its proximal end at the level of the seat ofthe main valve is identical to the area A of the cross-section of theinlet conduit measured at its end located near the flow control device.

A cross-section area C of the distal end of the outlet conduit isgreater than the cross-section area B of said cylindrical sectionmeasured in its proximal part.

Advantageously, the outlet conduit comprises, in the direction ofevacuation of the air, a convergent section 5A followed by a divergentsection 5B.

This arrangement makes it possible to increase the speed of the air atthe level of the narrowing, and hence to improve the blast.

A second arrangement used also makes it possible to improve the blast.

In order for the particularly truncated cup to open up the access to theoutlet conduit, it is necessary to evacuate the air contained in therear chamber 13 quickly.

To do this, conventionally, the device 14 is equipped with a so-calledevacuation valve 16 that controls the flow of the air contained in therear chamber 13 to the outlet conduit 5.

When the air from this rear chamber 13 is evacuated, the main valve 2Amoves back so as to open the passage.

According to the invention, the seat 17 of this evacuation valve 16 islocated at the level of the front face 2C of the cup or main valve, andin order to evacuate the air contained in the rear chamber, theevacuation valve 16 moves forward, in the direction opposite that of themain valve 2A as it leaves it seat.

This technical disposition is very advantageous.

In fact, the noise induced by the release of the air contained in therear chamber is no longer perceived and merges with the blast because itis not sent to the outside as it was before.

The second advantageous point consists in the fact that the forwardmovement of the valve each time eliminates any possible accumulations onthe front face of the cup.

A third advantage consists in the fact that the evacuation valve 16 isseparate from the cup 2A so that the latter is lighter and can thereforemove back faster.

This evacuation valve 16 is borne by the end of a control rod 16Atranslationally guided through the truncated cup.

The end of this valve rod 16A is connected to a drive means 20 forinducing its movement.

In one embodiment, the drive means 20 is an electromechanical devicethat presses on or drives the valve rod in the desired direction.

In another embodiment, this drive means 20 is a deformable membranewhich, when subjected to a pressure exerted in a so-called controlchamber 21, can move so as to drive the movement of the rod.

A chamber 22, located opposite the one that produces the opening for theevacuation of the air, is supplied with air at the same pressure as therear chamber in order to facilitate holding the valve 16 in its seat.

The valve rod 16A thus passes through the guide and the slider.

A return spring 23 returns the valve into position in its seat.

This return spring is housed in a bore included in the guide.

As may be seen, this guide is supported by the rear face of the body ofthe blast device.

In order to transfer the air contained in the rear chamber 13 to theopening bordered by the seat of the evacuation valve, the truncated cuphas evacuation channels 25 that open into a so-called front chamber 26housing a part of the valve.

Advantageously, the concave part of the cup 2A forms a part delimiting atrough 30 whose concavity turned toward the rear of the body of thedevice facing the guide 11 forms with the guide, in the retractedposition of the truncated cup, a so-called compression chamber 31forming a buffer for the backward movement of said cup.

A return spring of the particularly truncated cup 2A presses the latterinto its seat.

As may be seen in FIG. 2, the cup 2A includes three stages.

The rear stage is cylindrical in rotation with a radius that is constantalong the longitudinal axis.

The other two stages are also cylindrical in rotation, but the radiusvaries along the longitudinal axis, sharply decreasing toward the frontof the cup.

The seat 2B of the cup 2A is machined into the body of the device, butpreferably, this seat is formed by a collar 120 mounted inside the bodyof the device in order to facilitate maintenance (FIG. 5).

Another variant (FIG. 6) consists of providing a collar 121 mounted onthe cup 2A.

These collars 120 or 121 are made of a material that is less hard thanthose that come into contact with the opposing part.

As may be seen in FIG. 4, a gasket 40 is provided on the rear stage.

This gasket, which is not expected to provide a perfect seal, reducesthe working clearance to about two- to three-tenths of a millimeter.

The clearance of each side can therefore be greater, which prevents thepiston or the cup from jamming.

In one advantageous embodiment (FIG. 6), instead of having the rearstage of the cup 2A cooperate with a slight working clearance with thebody of the device, this rear stage cooperates with a liner 41, thisliner being mounted inside the body, though preferably this liner issupported by the rear wall.

While this invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the preferred embodiments of the invention as set forthherein, are intended to be illustrative, not limiting. Various changesmay be made without departing from the true spirit and full scope of theinvention as set forth herein.

1. Air blast device comprising an air flow control device disposedbetween an inlet conduit (3) adapted for connection to a container thataccumulates a volume of air and an outlet conduit (5), the outletconduit having a cross section area (C) measured at its distal endgreater than a cross-section area (A) of the inlet conduit measured atits end located adjacent the flow control device, and the outlet conduitfurther having, in the direction of evacuation of the air, a cylindricalsection (B) followed by a convergent section (5A) followed by adivergent section (5B).
 2. Air blast device according to claim 1,characterized in that the outlet conduit has a cross-section area (B)measured at its proximal end at the level of a seat of a piston or cupdisposed on the air flow path between the inlet and outlet conduitsidentical to the area (A) of the cross-section of the inlet conduitmeasured at its end located adjacent the flow control device.
 3. Airblast device according to claims 1 through 3 comprising an evacuationvalve (16) that controls the flow of the air contained in a rear chamberof a main valve to the outlet conduit through the movement of a piston(2A) in the shape of a cup, said evacuation valve (16) having a seat(17) located at the level of a front face (2C) of the cup, and in orderto evacuate the air contained in the rear chamber, the evacuation valve(16) adapted to move in a forward in a forward direction opposite thatof the cup (2A) as it leaves its seat.
 4. Air blast device according toclaim 3, characterized in that the evacuation valve (16) is supported bythe end of a control rod translationally guided through a truncated cupand an end of said control rod connected to a drive for inducingmovement of the control rod.
 5. Air blast device according to claim 4,characterized in that the drive (20) is an electromechanical device thatdrives the valve rod in a desired direction.
 6. Air blast deviceaccording to claim 4, characterized in that the drive (20) is adeformable membrane which, when subjected to a pressure exerted in acontrol chamber (21), deforms to drive the movement of the valve rod(16A).
 7. Air blast device according to claim 4, characterized in thatthe cup (2A) includes a concave part forming a through (30) whoseconcavity is turned toward the rear of the body of the device facing aguide, and said through (30) and the guide form, in a retracted positionof the cup, a compression chamber (31) forming a buffer for backwardmovement of said cup.
 8. Air blast device according to claim 3,characterized in that the seat (2B) of the cup or piston (2A) comprisesa collar (120) mounted inside the body of the blast.
 9. Air blast deviceaccording to claim 3, characterized in that a collar (121) is mounted onthe cup (2A).
 10. Air blast device according to claim 2, characterizedin that the outlet conduit comprises, in the direction of evacuation ofthe air, a convergent section (5A) followed by a divergent section (5B).11. Air blast device according claim 2, comprising an evacuation valve(16) that controls flow of the air contained in a rear chamber of a mainvalve to the outlet conduit through the movement of a piston (2A) in theshape of a cup, said evacuation valve (16) having a seat (17) located atthe level of the front face (2C) of the cup, and in order to evacuatethe air contained in the rear chamber, the evacuation valve (16) adaptedto move in a forward direction opposite that of the cup (2A) as itleaves its seat.
 12. Air blast device according claim 1, comprising anevacuation valve (16) that controls flow of the air contained in a rearchamber of a main valve to the outlet conduit through the movement of apiston (2A) in the shape of a cup, said evacuation valve (16) having aseat (17) located at the level of a front face (2C) of the cup, and inorder to evacuate the air contained in the rear chamber, the evacuationvalve (16) adapted to move in a forward direction opposite that of thecup (2A) as it leaves its seat.
 13. Air blast device according to claim11, characterized in that the evacuation valve (16) is supported by theend of a control rod translationally guided through a truncated cup andan end of said control rod connected to a drive for inducing movement ofthe control rod.
 14. Air blast device according to claim 12,characterized in that the evacuation valve (16) is supported by the endof a control rod translationally guided through a truncated cup and anend of said control rod connected to a drive for inducing movement ofthe control rod.
 15. Air blast device according to claim 13,characterized in that the drive (20) is an electromechanical device thatdrives the valve rod in a desired direction.
 16. Air blast deviceaccording to claim 14, characterized in that the drive (20) is anelectromechanical device that drives the valve rod in a desireddirection.
 17. Air blast device according to claim 4, characterized inthat the drive (20) is a deformable membrane which, when subjected to apressure exerted in a control chamber (21), deforms to drive themovement of the valve rod.
 18. Air blast device according to claim 13,characterized in that the cup (2A) includes a concave part forming atrough (30) whose concavity is turned toward the rear of the body of thedevice facing a guide, and said trough (30) and the guide form, in aretracted position of the cup, a compression chamber (31) forming abuffer for backward movement of said cup.
 19. Air blast device accordingto claim 11, characterized in that the seat (2B) of the cup or piston(2A) comprises a collar (120) mounted inside the body of the blastdevice.
 20. Air blast device according to claim 11, characterized inthat a collar (121) is mounted on the cup (2A).